1. Field of the Invention
The present application relates in general to oil and gas drilling operations, and in particular to an improved method and apparatus for monitoring the operating conditions of a downhole drill bit during drilling operations.
2. Description of the Prior Art
The oil and gas industry expends sizable sums to design cutting tools, such as downhole drill bits including rolling cone rock bits and fixed cutter bits, which have relatively long service lives, with relatively infrequent failure. In particular, considerable sums are expended to design and manufacture rolling cone rock bits and fixed cutter bits in a manner which minimizes the opportunity for catastrophic drill bit failure during drilling operations. The loss of a cone or cutter compacts during drilling operations can impede the drilling operations and necessitate rather expensive fishing operations. If the fishing operations fail, side track drilling operations must be performed in order to drill around the portion of the wellbore which includes the lost cones or compacts. Typically, during drilling operations, bits are pulled and replaced with new bits even though significant service could be obtained from the replaced bit. These premature replacements of downhole drill bits are expensive, since each trip out of the wellbore prolongs the overall drilling activity, and consumes considerable manpower, but are nevertheless done in order to avoid the far more disruptive and expensive fishing and side track drilling operations necessary if one or more cones or compacts are lost due to bit failure.
The present invention is directed to an improved method and apparatus for monitoring and recording of operating conditions of a downhole drill bit during drilling operations. The invention may be alternatively characterized as either (1) an improved downhole drill bit, or (2) a method of performing drilling operations in a borehole and monitoring at least one operating condition of a downhole drill bit during drilling operations in a wellbore, or (3) a method of manufacturing an improved downhole drill bit.
When characterized as an improved downhole drill bit, the present invention includes (1) an assembly including at least one bit body, (2) a coupling member formed at an upper portion of the assembly, (3) at least one operating condition sensor carried by the improved downhole drill bit for monitoring at least one operating condition during drilling operations, and (4) at least one electronic or semiconductor memory located in and carried by the assembly, for recording in memory data pertaining to the at least one operating condition.
The present invention may be characterized as in improved drill bit for use in drilling operations in a wellbore. The improved drill bit includes an number of components which cooperate. A bit body is provided which includes a plurality of bit heads, each supporting a rolling cone cutter. A coupling member is formed at an upper portion of the bit body. Preferably, but not necessarily, the coupling member comprises a threaded coupling for connecting the improved drill bit to a drillstring in a conventional pin-and-box threaded coupling. The improved drill bit may include either or both of a temperature sensor and a lubrication system sensor.
More particularly, the present invention relates to a number of alternative mechanical and electrical subsystems in a rockbit constructed in accordance with the present invention. One subsystem relates to the housing of the electronic components. In one particular embodiment, an electronics module is housed in a recess formed in a shank portion of the rockbit. A tight-fitting cap is provided to engage the interior surface of the shank. Seals, such as O-ring seals, are provided at the interface between the tight-fitting cap and the interior surface of the rock bit shank. A generally annular electronics cavity is formed and/or defined in part by the tight-fitting cap and the interior surface of the rock bit shank. Preferably, a printed circuit board may be maintained in the cavity.
In another particular embodiment, the electronics module is encapsulated in a fluid tight material in order to protect the electronics from exposure to fluids which may impair the operation of electronics or shorten the operating life of the electronics. When employed, the encapsulating material leaves only the wiring connections for, and to, the other electronic components in an exposed condition. For example, the wires which connect to sensors disposed in predetermined locations within the rock bit are provided and are accessible from the exterior of the encapsulating material. Furthermore, wires or terminals which connect to the battery carried by the improved rock bit are also accessible from the exterior of the encapsulated material. Other wires or terminals which allow for testing of the circuit and/or the downloading of recorded data are also accessible from the exterior of the encapsulated circuit and/or circuit board. This is advantageous over the prior art, insofar as it allows the electronics module to be handled in the field without substantial risk of impairment or injury to electrical components carried therein. Furthermore, it protects the circuit components from vibration damage, temperature damage, and fluid damage, any of which could occur without the extra protection provided by the capsulating material. In summary, the complexity of the assembly is reduced since the operator is supplied with one pre-wired and ready-to-install component, while the components are protected from damage.
In another particular embodiment, an improved grease sensor is provided which detects the ingress of non-lubricant fluids into the lubrication system of the improved rock bit.
In an alternative embodiment, an improved auxiliary nozzle configuration is provided which allows for signaling to a surface location. This new nozzle includes a relatively small, electrical-actuable piston member which is utilized to rupture a sealing disk when in an alarm condition is detected. The electrically-actuable piston device includes a piston member, a stationary cylinder member, an electrically-actuable ignition system, and terminals for connecting the electrically-actuable piston member to other components, such as the monitoring circuitry carried preferably in the shank portion of the improved drill bit.
In the particular embodiment discussed herein, alternative wiring paths are provided which allow for the electrical connection between monitoring components and sensors which improve over alternative wiring configurations. Essentially, the wiring channels are provided within each bit leg and extend downward from the shank portion to a medial portion of the bit leg for electrical connection to grease monitoring sensors. An additional channel is provided for connecting a battery located in a battery bay to the monitoring circuit which is carried in the shank portion of the drill bit.
Additionally, in the preferred embodiment, a switch is provided which may be actuated from the exterior portion of the bit which is utilized to turn the device on and off at specific instances in the drilling operation. This preserves battery life when monitoring is not necessary.
The above as well as additional objectives, features, and advantages will become apparent in the following description.